Battery controller and method for controlling a battery

ABSTRACT

A battery controller for charging and discharging a plurality of batteries is disclosed. The battery controller has a plurality of direct current to direct current (DC to DC) converters connected to each other in series. Each battery of a plurality of batteries is electrically connectable to a respective DC to DC converter. A co-ordinator connected to each of the plurality of DC to DC converters controls charging and discharging of the battery electrically connected to the respective converter. The coordinator can also control charging and discharging of any one of the batteries to ensure that the battery retains sufficient electrical capacity, and, to increase the longevity of the respective batteries. Because each battery is electrically connected to a respective DC to DC converter, the energy from one battery can be used to charge another battery in order to monitor battery characteristics including energy capacity of each battery. Each of the DC to DC converters is selected to operate preferably below 30 volts while the total voltage of the entire battery system can be much more than 30 volts depending on the number of DC to DC converters placed in series.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.10/793,951 filed Mar. 8, 2004, and hereby claims associated benefitsunder 35 U.S.C. section 120.

FIELD OF THE INVENTION

This invention relates to battery controllers and methods forcontrolling batteries. More particularly, the present invention relatesto battery controllers used to control batteries and/or power convertersconnected in series to provide power to a load.

DESCRIPTION OF THE RELATED ART

There is a growing trend for use of batteries, such as lithium ionbatteries and lead acid batteries, to power various devices, as diverseas electric cars, computers and cameras. There is also a growing trendto use batteries as an alternate or emergency power source, such as fortelephone systems, cable systems and other forms of communicationsystems or computer systems. The use of batteries helps ensure that asystem will survive power failures without interruption or damage to theunderlying system, or, loss of data or communication. This isparticularly important for emergency communication which is essentialduring power failures. In order to provide current and voltage atrequired levels for particular loads, regardless of the type of batterybeing used, it is known to have direct current to direct current (DC toDC) converters as well as other types of power converters. Theconverters both protect the load from the battery and/or the batteryfrom the load. Furthermore, the converters convert the power from thebattery to a form which can be used by the load. Some advancedrechargeable battery systems permit the same DC to DC converter to beused in reverse in order to recharge the battery.

Before proceeding to a discussion of DC to DC converter systems, a noteon the converter terminology used herein will now be given. Powerconverters have at least two sets of electrical terminals. One set ofpower converter terminals is generally connected (directly orindirectly) across one or more batteries. This set of power converterterminals will herein be called the battery-side terminals. The otherset of power converter terminals is generally connected (directly orindirectly) across a load or across an electrical power source forcharging the batteries. This set of power converter terminals willherein be called the load-side terminals, even if they are connectedacross a battery charging power source. FIGS. 1A and 1B illustrateconventional controllers for controlling batteries. In particular, FIG.1A illustrates a prior art system, identified generally by referencenumeral 2, comprising a DC to DC converter 8 for converting electricalpower from battery 6 and for supplying the converted electrical poweracross terminals 8 a and 8 b. As illustrated in FIG. 1A, the voltageacross the DC to DC converter 8 (called voltage V in FIG. 1A) may notnecessarily be the same as the battery 6 voltage V_(bat).

FIG. 1B also illustrates a prior art system, illustrated generally byreference numeral 3 and comprising three batteries 6 connected in serieswith a single DC to DC converter C₁ connected across all of thebatteries 6. In this way, the DC to DC converter C₁ can convert thepower from all of the batteries B to a useful form either for a load(not shown) or for use by a further converter C₂. The voltage V acrossthe output side of converter C₁ as well as the output side of converterC₂ may not be equal to the total voltage V_(a)+V_(b)+V_(c) across allthree of the batteries 6. One advantage of this system illustrated inFIG. 1B is that a single converter C₁ may be used regardless of thenumber of batteries B. However one disadvantage of this system arisesbecause the converters C₁ and C₂ are each connected across a wholeseries of three batteries 6. This type of power converter connectionprevents or limits the ability to monitor and to test the individualbatteries 6 connected in series. Furthermore, as is known to personsskilled in the art, if one of the batteries 6 fails, then it is notpossible to transfer any current through the failed battery with thepotential result that all batteries connected in series may fail if asingle battery in the series fails. One manner in which to overcome thisproblem would be to have a bypass circuit, such as the one includingresistor R₁ illustrated in FIG. 1B. This kind of bypass circuit allowspower to be communicated from or to the three batteries in the eventthat the associated battery fails. However, bypass circuits can beexpensive and difficult to implement and may not be tested for a numberof years or until its associated battery 6 fails. This infrequenttesting means that the circuit may not be operating at a time ofemergency.

By way of example, U.S. Pat. No. 6,377,024 to Choy discloses a methodand system to charge and discharge lithium ion batteries having aplurality of cells in series. This system utilizes a central dischargecontroller and a central charge controller to discharge and charge thebatteries while maintaining equalized charge at each cell. However, asystem such as this, which has a centralized discharger and charger,suffers from the disadvantage that it is difficult or impossible toindividually control the charging or discharging of each cell.

Furthermore, having centralized control leaves the entire system open tofailure should a single cell fail. In general, it is not possible tohave current pass through a battery or cell which has failed. If asingle battery of Choy's system fails, then the entire Choy system willfail, generally requiring replacement or other service.

U.S. Pat. No. 5,773,962 to Nor discloses a long chain battery forsupplying power to a load such as an electric vehicle. The main controlmodule and a plurality of battery modules are provided. Each batterymonitoring module will monitor a number of batteries and the currentcarrying wire between them, so that incipient problems may be detectedbefore failure or significant damage occurs. However, Nor also fails todisclosure monitoring each battery individually as opposed to a numberof batteries collectively. Furthermore, Nor fails to disclose a suitablemeans to deal with a failure which may be detected because Nor's batterymonitoring system treats two whole sets of batteries and it's connectingcircuitry as a single unified entity.

Several publications disclose systems with multiple batteries andmultiple DC to DC converters, where the load-side terminals of the DC toDC converters are connected with each other in parallel. Thesepublications include: (1) U.S. patent application publication number2003/0107906 to Tokunaga et al. (uninterruptible power supply withrechargeable batteries); (2) U.S. patent application publication number2003/0091882 to Schmidt et al. (fuel cell batteries); and (3) U.S.patent application publication number 2002/0070705 to Buchanan et al.(vehicle charging system). In the Buchanan et al. vehicle chargingsystem, it is noted that the DC to DC converters can drain selectedbatteries to obtain power to charge other batteries, allowing forbatteries to be cycled.

U.S. patent application publication number 2001/0049038 to Dickman etal. discloses a fuel cell system with a plurality of fuel cell stacks.The Dickman et al. system is uses a hydrogen gas stream to produceelectrical power for various loads, such as vehicles, boats, lights,microwave relay stations and communication equipment. The Dickman et al.system features redundant fuel cell stacks, where a plurality of fuelcell stacks delivers the same, or greater, maximum rated power output asa comparable single-stack fuel cell system.

In some embodiments of the Dickman et al. system, each fuel stack isrespectively connected to a DC to DC converter. As stated in the Dickmanet al. published application, the regulated DC output from these DC toDC converters may be connected in parallel or series. For presentpurposes, discussion shall focus on the disclosed Dickman et al.embodiment where the output of DC to DC converters are connected inseries. It is noted that Dickman et al. does not disclose the use of anysort of fuel-less battery, as the fuel stacks of Dickman et al. utilizehydrogen gas as a fuel. It is further noted that Dickman et al. does notdisclose the use of any sort of rechargeable battery, as the fuel stacksof Dickman et al. utilize a continuing hydrogen stream to generate itselectrical power. (See DEFINITIONS section below for definitions of“fuel-less battery” and “rechargeable battery.”) Also, because the fuelcell stacks of Dickman et al. uses a continuous stream of hydrogen gasfor fuel, they do not have energy capacities the way that fuel-lessbatteries do.

In the Dickman et al. device, each fuel stack, and associated, dedicatedDC to DC converter has only two operational states, off and on. If agiven fuel cell stack and associated DC to DC converter is off, then thefuel cell stack does not produce current and its DC to DC converter willnot convert power from the turned-off fuel stack. If a given fuel cellstack and associated DC to DC converter is on, then the DC to DCconverter is controlled so that its output voltage matches somepredetermined value. This predetermined output voltage value isdisclosed to depend only on whether the output voltage is being appliedto a battery assembly or, alternatively, to a load of a device. Thepredetermined output voltage is not disclosed to depend upon theoperational status of its associated fuel cell or any of the other fuelcells in the system. The predetermined output voltage is also notdisclosed to vary among the DC to DC converters that happen to be on ata given time.

Description Of the Related Art Section Disclaimer: To the extent thatspecific publications are discussed above in this Background section,these discussions should not be taken as an admission that the discussedpublications (e.g., patents) are prior art for patent law purposes. Forexample, some or all of the discussed publications may not besufficiently early in time, may not reflect subject matter developedearly enough in time and/or may not be sufficiently enabling so as toamount to prior art for patent law purposes.

SUMMARY OF THE INVENTION

There is still need for improved battery control and for battery-poweredsystems that can easily survive failure of one or more of the batteries.There is also a need for a battery controller and a method ofcontrolling batteries which can periodically test and/or charge anddischarge batteries in order to ensure that they are operatingcorrectly, especially for backup systems which may not be used for anumber of years or until an emergency arises. Furthermore, it isdesirable to provide battery controllers at the lowest feasible cost.

Accordingly, it is an object of some embodiments of this invention to atleast partially overcome some of the disadvantages of the prior art.Also, it is an object of some embodiments of this invention to provide abattery controller and a method for controlling batteries which cansurvive failure of one or more of the batteries. Furthermore, it is anobject of some embodiments of the present invention to provide a batterycontroller and method which has increased robustness. Furthermore, it isan object of some embodiments of this invention to provide a systemwhich can individually control and monitor each battery amongst aplurality of batteries to ensure that the batteries are operatingcorrectly, and, to increase the longevity of each of the batteries.

One aspect of the present invention is an apparatus for providingelectrical power. The apparatus includes fuel-less batteries and twobattery power converters. The fuel-less batteries are structured todischarge and thereby supply electrical power. The first battery powerconverter includes battery-side terminals and load-side terminals. Thebattery-side terminals of the first battery power converter areconnected across at least one fuel-less battery of the plurality offuel-less batteries. The second battery power converter includesbattery-side terminals and load-side terminals. The battery-sideterminals of the second battery power converter are connected across atleast one fuel-less battery of the plurality of fuel-less batteries. Theload-side terminals of the first and second battery power converters areelectrically connected to each other in series.

Another aspect of the present invention is apparatus for storing anddischarging electrical power. The apparatus includes rechargeablebatteries and two battery power converters. The rechargeable batteriesare structured to store and discharge electrical power. The firstbattery power converter includes battery-side terminals and load-sideterminals. The battery-side terminals of the first battery powerconverter are connected across at least one rechargeable battery of theplurality of rechargeable batteries. The second battery power converterincludes battery-side terminals and load-side terminals. Thebattery-side terminals of the second battery power converter areconnected across at least one rechargeable battery of the plurality ofrechargeable batteries. The load-side terminals of the first and secondbattery power converters are electrically connected to each other inseries.

Another aspect of the present invention is an apparatus for providingelectrical power. The apparatus includes batteries two battery powerconverters and two battery power diagnostic devices. The batteries arestructured to discharge and thereby supply electrical power. Thebatteries include at least a first battery subset and a second batterysubset. The first battery subset and the second battery subset are notidentical subsets. The first battery power converter includesbattery-side terminals and load-side terminals. The battery-sideterminals of the first battery power converter are connected across thefirst battery subset. The first battery power diagnostic device isconnected across the first battery subset. The second battery powerconverter includes battery-side terminals and load-side terminals. Thebattery-side terminals of the second battery power converter areconnected across the second battery subset. The second battery powerdiagnostic device is connected across the second battery subset.

Another aspect of the present invention is an apparatus for providingelectrical power. The apparatus includes batteries, battery powerconverters and control circuitry. The batteries are structured todischarge and thereby supply electrical power. The battery powerconverters are electrically connected to the plurality of batteries sothat the electrical discharge of the plurality of batteries suppliespower to the battery power converters. The control circuitry isstructured and located to control the battery power converters so thatat least two of the plurality batteries will discharge at substantiallythe same rate.

Accordingly, one advantage of some embodiments of the present inventionis that, because the batteries are not connected in series, but ratherthe converters are connected in series, failure of any one battery willnot cause current flowing through any other battery to cease. Rather,because the converters are connected in series as opposed to thebatteries being connected in series, failure of any one battery caneasily be corrected by permitting current to flow through the converter.Converters, unlike batteries, usually permit current to flow throughthem even when the battery associated with the converter is notoperating. Accordingly, this increases the flexibility and robustness ofthe overall battery controller and battery system.

A further advantage of some embodiments of the present invention isthat, by having each DC to DC converter electrically connectable to arespective battery of the plurality of batteries, the converter can alsomonitor the voltage and/or current coming from its corresponding batteryin order to better assess whether or not it has failed, will fail or isoperating improperly. This increases the robustness of the system byproviding information on each battery to attempt to make earlypredictions of battery failure.

A further advantage of some embodiments of the present invention isthat, because each DC to DC converter is electrically connectable to arespective battery of the plurality of batteries, it is possible to havean individual battery charged and discharged, regardless of the statusof the other batteries. This could be used, for example, to periodicallydischarge a battery and then recharge it to ensure that the battery isoperating properly. This is potentially important because failure toperiodically discharge and charge batteries of some chemistries, couldadversely affect the capacity of the disused battery. For instance, andin particular, if the batteries are being used for backup, or, if thebatteries are not discharged for 1, 2 or 5 years, it is possible thatthe total energy capacity of the batteries will decrease and degradeeven if the voltage across the batteries remains the same. Therefore, bydischarging and charging the batteries, not only is the true energycapacity of the battery easily determined, but the mere process ofdischarging and recharging the batteries could greatly increase thelongevity and energy capacity of the batteries.

A further advantage of the present invention is that in some preferredembodiments, the batteries are arranged such that the maximum nominalvoltage across any battery and therefore across any DC to DC converteris preferably in the range of 5 volts to 30 volts, more preferably inthe range of 10 volts to 25 volts and still more preferably in the rangeof 15 volts to 22 volts.

Consider a battery-powered system where the total number of batteries isrepresented by N, and if the total expected voltage during nominaldischarge for the battery system is represented by the V_(total), andeach battery contributes approximately an equal share of the totalpower. In this preferred embodiment, the voltage of any one DC to DCconverter is approximately V_(total)/N. preferably, this V_(total)/Nvalue is less than 30 volts so that low-voltage, low-cost DC to DCconverters can be used. In this way, while a larger number of convertersmay be required in order to implement the battery controller, theconverters can be used in the lower voltage range, which tends to bemore economical and often more energy efficient. Therefore, even thougha larger number of DC to DC converters may be required, the total costmay not be significantly greater than a single converter. This costbenefit is especially likely if the rated voltage of the DC to DCconverters is in the preferred ranges set forth above.

Further aspects of the invention will become apparent upon reading thefollowing detailed description and drawings, which illustrate preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate embodiments of the invention:

FIG. 1A illustrates a conventional battery controller having a singlebattery;

FIG. 1B illustrates a conventional battery controller for controllingmore than one battery;

FIG. 2 is a schematic diagram according to a first embodiment of thepresent invention;

FIG. 3A illustrates a DC to DC converter which can be used in a systemillustrated in FIG. 2 having a buck/boost operation according to oneembodiment of the present invention;

FIG. 3B illustrates a DC to DC converter which can be used in a systemillustrated in FIG. 2 having a buck operation according to oneembodiment of the present invention;

FIG. 3C illustrates a DC to DC converter which can be used in a systemillustrated in FIG. 2 having a boost operation according to oneembodiment of the present invention;

FIG. 3D illustrates a DC to DC converter which can be used in a systemillustrated in FIG. 2 having a buck/boost four quadrant operationaccording to one embodiment of the present invention;

FIG. 4 is a schematic diagram of a second embodiment of the presentinvention; and

FIG. 5 is a schematic diagram of a device where two DC to DC convertersare connected in parallel.

FIG. 6 is a schematic diagram of a third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Battery controller apparatus 200, an embodiment of the presentinvention, is shown in FIG. 2 and will now be discussed. Apparatus 200is designed to charge, recharge and discharge several batteries B(individually identified by reference numerals 61 to 64). Apparatus 200further includes several DC to DC converters, shown generally by theletter C (identified individually by reference numerals 201, 202, 203and 204). As illustrated in FIG. 2, the DC to DC converters areconnected to each other in series. Each DC to DC converter C is alsorespectively electrically connected to a battery B selected from the setof batteries. In preferred embodiment 200, the batteries B are notelectrically connected (or necessarily connectable) to each other. Inalternative embodiments, there may be various series and/or parallelconnections among some or all of the batteries. A potential drawback ofthese alternative embodiments is that failure of one or more of theconnected batteries will tend to have a greater adverse effect on thesystem (e.g., on other batteries) than failure of a relatively isolatedbattery as in preferred embodiment 200. Nevertheless, there may beapplications where it is acceptable, or even preferable, to have variouselectrical connections among some or all of the batteries, dependingprimarily upon the power, cost and/or reliability requirements of thesystem. Even though FIG. 2 illustrates four batteries 61 to 64 and fourrespective converters 201 to 204, it is understood that the invention isnot limited to this number, but rather could be applied to any systemincluding two or more batteries.

As also illustrated in FIG. 2, a co-ordinator 220 is connected to eachof the plurality of DC to DC converters C. The co-ordinator 220 sendscontrol signals to the DC to DC converters C for controlling thecharging and discharging of the respective battery 61, 62, 63, 64.Preferably, the control signals are sent through the electricalconnection 222, which may be structured as a computer bus. However, thecontrol signals could also be sent by any other manner, includingwirelessly or at different frequencies together with the DC currentI_(total) across terminals 230.

In this way, the power from each of the batteries B will pass to itsrespective converter C and the converted power will then pass to theterminals 230. Terminals 230 can be connected to power one or more loadsso that electrical power can be transferred from the batteries B to oneor more loads L. Furthermore, the terminals 230 could be connected to apower source (not shown) to assist in recharging the batteries B,assuming the batteries are rechargeable.

In operation, a single DC to DC converter would be electricallyconnectable to a respective battery of the plurality of batteries. If,for whatever reason, one DC to DC converter C does not have a respectivebattery to be connected to, the DC to DC converter C would operatesimply as a short circuit to allow power and current from the other DCto DC converters C to flow through it without interruption. Although DCto DC and other power converters are usually able to operate as a bypassin this way, it is to be understood that bypass functionality is not arequirement of all power converters or all embodiments of the presentinvention.

Likewise, if a battery connected to an associated DC to DC converter Cmalfunctions, current could still flow through the associated DC to DCconverter C without interruption, even though the respective battery Bhas malfunctioned. This avoids failure of the battery controller shoulda single battery malfunction.

Co-ordinator 220 co-ordinates the operation of the converter C in orderto control the charging and discharging of each battery by controllingeach respective converter. Co-ordinator 220 thereby selectively controlsthe discharging and charging of each battery in order to transferelectrical power from the plurality of batteries to one or more loads L.Similarly, co-ordinator 220 can selectively control the respective DC toDC converters C to co-ordinate charging of the batteries B.

In order to more efficiently control the batteries B through theirrespective DC to DC converters C, the co-ordinator may receiveinformation regarding the total voltage V_(total) and total currentI_(total) passing through the DC to DC converters C. Accordingly, thecontroller embodiment 200 comprises a sensor 210. Sensor 210 may sensetotal current I_(total), voltage V_(total) and/or other characteristicsof the electrical power being output. In a preferred embodiment, each ofthe DC to DC converters C sense the voltage passing across therespective batteries B and send this information to co-ordinator 220through electrical connection 222. It is also understood that V_(total)represents the sum of the voltage across all of the converters C andthis may not necessarily be the same at the sum of the voltages(V₁+V₂+V₃+V₄) across the batteries B because the converters C willlikely have converted the voltage of their respective batteries.

In addition to co-ordinator 220 controlling the discharging and chargingof a plurality of batteries to transfer electrical power from theplurality of batteries to one or more loads, co-ordinator 220 can alsocontrol the DC to DC converter C in order to affect a particular onebattery of the plurality of batteries. For instance, the co-ordinator220 can send a signal D₂ to one of the plurality of DC to DC convertersC, such as converter 202. The signal D₂ can instruct converter 202 tocommence discharging battery 62, which is electrically connected to theconverter 202. In this way, co-ordinator 220 can monitor the dischargeof battery 62 to ensure that battery 62 is discharging or otherwiseoperating correctly in order to ensure that battery 62 is available foruse in the future.

This can be particularly useful, as indicated above, in backup batterysystems which may not be used for extended periods of time. Testingcapacity of each battery is important because a battery may not have theelectrical capacity that is expected and/or needed. Furthermore, manybatteries require periodic discharging and charging in order to improvetheir longevity and electrical capacity. Therefore, co-ordinator 220, inaddition to periodically discharging a specific battery for testing, canalso periodically discharge and then recharge one or more of thebatteries to improve their longevity and better maintain energycapacity.

It is noted that co-ordinator 220 could discharge a particular batterywhenever the need arises to service an external load. However, in thecase of a backup system, co-ordinator 220 may simply transfer electricalenergy from one battery, such as battery 61 to a subsequent battery,such as battery 62, in order to discharge and charge the batteries in aperiodic fashion. This could be performed, for example, through a closedloop of all of the converters C by co-ordinator 220 closing a switch,such as backup switch 250. If no backup switch 250 is present, then itmay be possible to perform the foregoing kind of energy transfer betweenbatteries only when running current through terminals 230 and loads 150,151.

The deliberate transfer of electrical energy between batteries can helpprovide diagnostic information about how much capacity each battery has.If a battery is intentionally discharged completely, and its energyoutput is measured over the interval of the discharge, then the capacityof the battery will be known. Of course, this can help provideinformation about how quickly a given battery is losing capacity and howsoon it may need to be serviced or replaced. In this way, someembodiments of the present invention may perform the function of aconventional battery cycling machine, wherein a battery's storagecapability is tested using these other batteries in the apparatus toprovide temporary energy storage.

It is understood that the DC to DC converters C can be any type of DC toDC converter which can be operated by co-ordinator 220 and used tocharge and discharge the batteries electrically connected to them.However, FIGS. 3A, 3B, 3C and 3D illustrate preferred embodiments of theDC to DC converters in buck boost and a buck/boost four quadrantoperation. It is understood that these are given merely by way ofexample and the present invention is not limited to the specificcircuits illustrated in FIGS. 3A to 3D.

Furthermore, it is understood that the circuits 3A to 3D contain anumber of switches S which operate in combination with the capacitorsand inductors shown therein to selectively charge and discharge thecorresponding battery. The signals used to operate the switches may comefrom a variety of sources. For example, the switches S can be operatedeither by co-ordinator 220 in response to signals along connection 222,or, in more sophisticated systems, by software present on each of therespective DC to DC converters C in response to signals received fromco-ordinator 220. Furthermore, in a preferred embodiment, the DC to DCconverters C may be used in reverse, namely to provide electrical powerto batteries B such as for recharging.

It is also noted that the present invention, as illustrated in the FIG.2, may include other devices and components including filters,capacitors, inductors and sensors, as is known in the art to operatebattery controller apparatus 200. These other devices and componentshave been omitted from the drawings for the sake of clarity ofillustration.

One important advantage of some embodiments of the present invention isthe ability to discharge a set of batteries at controlled rates. Forexample, it is often desirable to discharge batteries at the same ratewith respect to their remaining capacities, so that if the batteries arenot recharged, they will run down at approximately the same time.

These advantages of controlled rate of discharge and similar dischargerate will now be discussed with reference to the DC to DC converter 300of FIG. 3A. Consider an initial state for converter 300 where: (1) thebattery is fully charged; (2) switch S₁ is closed; and (3) switch S₂ isopen. Current will flow from the battery to charge capacitor 304.Current will also start to flow from the battery through inductor 306.

Now consider a first subsequent state for converter 300 where: (1)switch S₁ is opened; (2) switch S₂ is closed; and (3) terminals 310 areconnected to an electrical load. When the switches are switched to thisfirst subsequent state, current will continue to flow through theinductor, even though it has been electrically disconnected from battery302 and capacitor 304. This continuing flow of current through inductor306 will charge capacitor 308, with a polarity as indicated by the plusand minus signs shown at terminals 310. In addition to charging upcapacitor 308, some current will also flow through terminals 310 toprovide electrical power to the load. Again, the polarity of thiscurrent is shown by the plus and minus signs at load-side terminals 310.

If converter 300 remained in this first subsequent state then inductor306 would gradually stop supplying current, capacitor 308 woulddischarge and at some point converter 300 would stop supplyingelectrical power to the circuit. However, consider that the switches areswitched relatively quickly from this first subsequent state to a secondsubsequent state. In the second subsequent state: (1) switch S₁ is againclosed; (2) switch S₂ is open; capacitor 304 is charged; and (4)capacitor 308 is charged. In this second subsequent state, capacitor 304and the battery will tend to cause current to increase through inductor306 due to the closure of switch S₁. At this point, inductor 306 will beelectrically disconnected from the load due to the open state of switchS₂. Capacitor 308 will discharge to supply power to the load.

Now consider that converter is now alternated between the firstsubsequent state and the second subsequent state in a controlled manner.Inductor 306 will tend to have somewhat continuous current flow,alternately receiving current from capacitor 304 and the battery andsupplying current to capacitor 308 and the load. Significantly, thebattery will be discharged at a rate determined largely by theproportion of the time switch S1 is closed. If several DC to DCconverters are connected in series, then these converters can becontrolled in a co-ordinated manner so that the batteries discharge atproportionate rates. For example a first battery could be controlledthrough the apparatus of converter 300 to discharge its remainingcapacity twice as fast as another battery in the system (controlledthrough the apparatus of another DC to DC converter). This kind ofcontrolled discharge rates are preferably accomplished by connecting theload-sides of DC to DC converters (e.g., like converter 300) in serieswith each other.

Preferably, the batteries are controlled so that they will dischargetheir respective capacities in a roughly synchronous manner so that someor all of the batteries in the system will be discharged at roughly thesame time. This can be advantageous for both rechargeable andnon-rechargeable battery systems because it helps ensure that thecontrolled batteries will all discharge most or all of their electricityby the time battery recharge or replacement is required. This can beadvantageous for rechargeable battery systems because: (1) it helpsensure that no battery will run down completely in the interval betweenbattery recharges; and (2) it helps ensure that all of the batteries areundergoing charge/discharge cycles at roughly the same frequency so thatthe rechargeable batteries will all remain effective as long aspossible. Similarly, the recharge of rechargeable batteries can becontrolled so that charging occurs in a roughly synchronous manner andmultiple batteries finish recharging at approximately the same time.

There are potential advantages to discharging batteries in a roughlysynchronous manner. Roughly synchronous discharge means that theoperating time is maximized. Furthermore, for most batteries, faster thedischarge of the battery means that less energy can be discharged fromthe battery due to known transient phenomena inherent in batterychemistry and physics. When each battery is discharged at the same rate,relative to its capacity, then each battery will be discharging asslowly as possible consistent with providing the required power to theloads. Through this relatively slow battery discharge, the total energythat will be output will increase.

When multiple batteries are controlled to discharge at proportionaterates, the power output at the load-side terminals of the DC to DCconverters is effectively controlled to be proportionate. Because the DCto DC converters are connected in series, current control cannotgenerally be used to effect this proportionate discharge. Rather, theproportionate discharge (or recharge) is preferably effected bycontrolling the voltage drop across the load-side terminals of eachconverter. However, in many applications, the voltage drop across theseries-connected set of Dc to DC converters must be regulated to havesome constant, predetermined value. This means that the co-ordinatorwill preferably control the voltage drop across each converter tosimultaneously: (1) achieve any desired proportionate battery discharge;and (2) maintain a constant, predetermined voltage drop across theseries-connected set of converters.

FIG. 4 illustrates an apparatus 400 for charging and/or dischargingbatteries. Apparatus 400 includes: (1) fuel-less, rechargeable batteriesB10, B12, B13, B14, B15; (2) converters C10, C11; (3) bypass circuitryR10; and (4) various electrical connections between the above-mentionedcomponents (as shown in FIG. 4). Apparatus 400 is not necessarily apreferred embodiment, but is provided to help give some idea of thepotential scope of the present invention.

As shown in FIG. 4, not all batteries apparatus 400 are subject to thepower conversion of a power converter. For example, battery B10 isconnected in series with the load-side terminals of converters C10 andC11. Battery B10 is associated with bypass circuitry R10, which bypasscircuitry helps protect the system in the case of failure of batteryB10. Battery B15 is also not subjected to power conversion as shown inFIG. 4. Of course, there may be severe problems with the apparatus ifbattery B15 fails because it is subject to neither power conversion norany other type of bypass circuitry.

As shown in FIG. 4, batteries B13 and B14 are connected in series. Thisseries-connected subset of batteries B13 and B14 is connected across thebattery-side of power converter C11. If either battery B13 or batteryB14 fails, then this subset will not be able to supply or receiveelectrical power. However, there is still some advantage here in thatbatteries B13 and B14 are somewhat isolated from the rest of apparatus400 from a power transfer and monitoring perspective.

FIG. 5 shows apparatus 500. Apparatus 500 includes coordinator component502, rechargeable battery B20, rechargeable battery B21, battery powerconverter C20 and battery power converter C21. Converter C20 includesbattery-side terminals 504 and load-side terminals 508. Converter C21includes battery-side terminals 506 and load-side terminals 510. Asshown in FIG. 5, battery B20 is connected to converter C20 throughbattery-side terminals 504. Battery B21 is connected to converter C21through battery-side terminals 506. Coordinator component 502 controlsthe operation of converter C20 and C21. Thereby, coordinator component502 indirectly controls the discharging and charging of the batteriesB20, B21.

In apparatus 500, the load side terminals 508, 510 are connected to eachother in parallel. By virtue of this parallel connection, coordinator502 can control the operation of converters C20 and C21 so that chargecan be moved in an arbitrary fashion between batteries B20 and B21. Thisallows the batteries to charge each other. This feature can be highlyadvantageous from a power management perspective because it can helpensure that neither battery B20 or B21 completely loses all charge.Because these batteries are connected in parallel, there is no need foradditional hardware similar to backup switch 250 (discussed above inconnection with FIG. 2).

FIG. 6 shows apparatus 600, which is a combination of two of apparatus500 connected in series with each other. Apparatus 600 includescoordinator component 602, rechargeable batteries B30, B31, B32, B33 andbattery power converters C30, C31, C32, C33. Converter C30 includesbattery-side terminals 604 and load-side terminals 612. Converter C31includes battery-side terminals 606 and load-side terminals 614.Converter C32 includes battery-side terminals 608 and load-sideterminals 616. Converter C33 includes battery-side terminals 610 andload-side terminals 618. As shown in FIG. 6, each battery B30, B31, B32,B33 is respectively connected to a dedicated battery power converterC30, C31, C32, C33 through battery-side terminals 604, 606, 608, 610.Coordinator component 602 controls the operation of converters C30, C31,C32, C33. Thereby, coordinator component 602 indirectly controls thedischarging and charging of the batteries B30, B31, B32, B33.

In apparatus 600, the load-side terminals of converters C30 and C31 areconnected in parallel with each other. Likewise, the load-side terminalsof converters C32 and C33 are connected in parallel with each other.These two parallel subsets of converters are electrically connected toeach other in series. The parallel connections may help facilitate theshifting of charge between batteries in the same parallel-connectedsubset. The series converter connection between the subsets can helpaggregate voltage from parallel-connected subsets of the batteries.Because the series connection is made between load-side terminals ofconverters, rather than between the batteries themselves, there areadvantages from the repair, replacement and monitoring perspectives asdiscussed in detail above. Other embodiments of the present inventionmay include varying numbers of batteries, varying numbers of batterypower converters and varying schemes of parallel and serial connectionsbetween the load-side terminals of the battery power converters.

Now that the embodiments of the Figures have been discussed, somepossible, exemplary applications for the power supplies of the presentinvention will now be discussed. In general, the present invention maybe advantageous in systems that require high voltage, adjustable voltageand rechargeable systems. Exemplary applications include electricvehicles, telephone transmission devices backup power supplies anduninterruptible power supplies.

It is noted that even though various features of the invention have beendescribed with respect to one or another of the embodiments of theinvention, the various features and embodiments of the invention may becombined or used in conjunction with other features and embodiments ofthe invention as described and illustrated herein. Also, although thisdisclosure has described and illustrated certain preferred embodimentsof the invention, it is to be understood that the invention is notrestricted to these particular embodiments. Rather, the inventionincludes all embodiments which are covered literally and/or by otherpatent law principles (e.g., the Doctrine of Equivalents) which may beapplicable in a given jurisdiction.

Definitions

The following definitions are to be used when construing an/orinterpreting the claims to the extent permitted by applicable law:

Battery: Any device which can chemically store and/or dischargeelectrical energy; batteries are not limited to any particular number ofcells (including a single cell), particular materials or material states(e.g., dry, wet, gel); batteries are not limited to devices which storeor output direct current (although most batteries currently operate onlywith direct current); examples of batteries include lithium ionbatteries fuel cells and lead acid batteries.

Fuel-less Battery: Any battery (see definition above), whetherrechargeable or not, that does not consume fuel. For example, a hydrogenfuel cell is not a fuel-less battery because hydrogen is the fuel and acontinuous stream of hydrogen is necessary for the fuel cell to operate.As further example, convention lead acid batteries, alkaline batteriesand lithium ion batteries are all fuel-less batteries. A fuel-lessbattery generally has a total energy capacity, representing the totalamount of energy it can store. A fuel-less battery generally also has aremaining energy capacity, representing the total amount of energy ithas left at a given time.

Rechargeable Battery: Any battery (see above definition) that can berecharged.

Inductor: Any electrical device put into a circuit for the purpose ofadding inductance into the circuit.

Capacitor: Any electrical device put into a circuit for the purpose ofadding capacitance into the circuit.

Battery power converter: any device structured to convert, in some waythe power input to or output from a battery or set of batteries; thisconversion is not limited to conversion of or to direct currentelectrical power; battery power converters may or may not include bypasscircuitry; battery power converters may or may not include coordinatorcomponents for selectively controlling battery charging and discharging;battery power converters may or may not include diagnostic devices formonitoring battery performance; examples of power conversion includevoltage conversion and current conversion.

Battery power diagnostic device: any device structured to monitor theperformance of a battery; battery power diagnostic devices may or maynot be coupled with battery power converters.

Connected Across: means electrically connected across; “connectedacross” covers both: (1) circuitry where the specified component(s) arethe exclusive component(s) connected across; and (2) circuitry where thespecified components are connected across along with other component(s)not specified in the patent claim.

1. An apparatus for charging and discharging a plurality of batteries,said apparatus comprising a plurality of batteries; a plurality ofdirect current to direct current (DC to DC) converters, each DC to DCconverter comprising load-side terminals and battery-side terminals,with the load-side terminals of the DC to DC converters being connectedto each other in series, and, each battery of the plurality of batteriesis electrically connected to the battery-side terminals of a respectiveDC to DC converter; a co-ordinator connected to each of the plurality ofDC to DC converters for controlling charging and discharging of thebattery electrically connected to the respective converter; and whereinthe series connected load-side terminals of the plurality of DC to DCconverters are electrically connected to at least one load and theco-ordinator co-ordinates the transfer of electrical power from theplurality of batteries to the one or more loads.
 2. The apparatus forcharging and discharging a plurality of batteries as defined in claim 1wherein each of the plurality of DC to DC converters operate in therange of 5 volts to 30 volts.
 3. The apparatus for charging anddischarging a plurality of batteries as defined in claim 2 wherein eachof the plurality of DC to DC converters operate in the range of 10 voltsto 25 volts.
 4. The apparatus for charging and discharging a pluralityof batteries as defined in claim 3 wherein each of the plurality of DCto DC converters operate in the range of 15 volts to 22 volts.
 5. Theapparatus for charging and discharging a plurality of batteries asdefined in claim 2 wherein: N represents the total number of DC to DCconverters in the plurality of DC to DC converters; V_(total) representsthe expected total voltage of the nominal discharge of the apparatus;the voltage of any one DC to DC converter is approximately V_(total)/N;and V_(total)/N is less than or approximately equal to 30 volts.
 6. Theapparatus for charging and discharging a plurality of batteries asdefined in claim 1 further comprising a current monitor for monitoringthe current passing through the plurality of DC to DC convertersconnected in series.
 7. The apparatus for charging and discharging aplurality of batteries as defined in claim 1 further comprising avoltage monitor for detecting the total voltage across the seriesconnected load-side terminals of the plurality of DC to DC converters.8-10. (canceled)
 11. A method for charging and discharging a pluralityof batteries, said method comprising: providing a plurality of nbatteries, where n is an integer greater than 1; providing a pluralityof n DC to DC converters, with each converter comprising load-sideterminals and battery-side terminals; electrically connecting thebattery-side terminals of each DC to DC converter of the plurality of DCto DC converters to a respective battery of the plurality of batteries;electrically connecting a co-ordinator to each of the plurality of DC toDC converters for controlling, charging and discharging each of therespective batteries; and wherein the load-side terminals of theplurality of DC to DC converters are electrically connected to eachother in series and the co-ordinator co-ordinates transfer of electricalpower from the respective batteries to one or more loads through theseries connected load-side terminals of the plurality of DC to DCconverters.
 12. An apparatus for providing electrical power, theapparatus comprising: a plurality of fuel-less batteries structured todischarge and thereby supply electrical power; a first battery powerconverter comprising battery-side terminals and load-side terminals,with the battery-side terminals of the first battery power converterbeing connected across at least one fuel-less battery of the pluralityof fuel-less batteries; and a second battery power converter comprisingbattery-side terminals and load-side terminals, with the battery-sideterminals of the second battery power converter being connected acrossat least one fuel-less battery of the plurality of fuel-less batteriesand with the load-side terminals of the first and second battery powerconverters being electrically connected to each other in series.
 13. Theapparatus of claim 12 wherein: each of the plurality of batteriesoutputs direct current power; the first battery power converter is a DCto DC converter; and the second battery power converter is a DC to DCconverter.
 14. The apparatus of claim 12 wherein the battery-sideterminals of the first battery power converter and the battery-sideterminals of the second battery power converter are connected acrossnon-identical sets of fuel-less batteries of the plurality of fuel-lessbatteries.
 15. The apparatus of claim 14 wherein: the battery-sideterminals of the first battery power converter are connected across afirst fuel-less battery of the plurality of batteries; and thebattery-side terminals of the second battery power converter areconnected across a second fuel-less battery of the plurality ofbatteries.
 16. The apparatus of claim 14 further comprising at least oneadditional battery power converter, wherein: the at least one additionalbattery power converter each comprises battery-side terminals andload-side terminals; and the battery-side terminals of each of the firstbattery power converter, the second battery power converter and eachadditional battery power controller being respectively connected acrossa unique battery from the plurality of fuel-less batteries.
 17. Theapparatus of claim 12 wherein the first and second battery powerconverters are voltage converters.
 18. The apparatus of claim 12 whereinthe first and second battery power converters are current converters.19. The apparatus of claim 12 wherein the first battery power convertercomprises bypass circuitry to allow the passage of electrical powerthrough the first battery power converter even in the absence of powersupplied at the battery-side terminals of the first battery powerconverter.
 20. An apparatus for storing and discharging electricalpower, the apparatus comprising: a plurality of rechargeable batteriesstructured to store and discharge electrical power; a first batterypower converter comprising battery-side terminals and load-sideterminals, with the battery-side terminals of the first battery powerconverter being connected across at least one rechargeable battery ofthe plurality of rechargeable batteries; and a second battery powerconverter comprising battery-side terminals and load-side terminals,with the battery-side terminals of the second battery power converterbeing connected across at least one rechargeable battery of theplurality of rechargeable batteries and with the load-side terminals ofthe first and second battery power converters being electricallyconnected to each other in series.
 21. The apparatus of claim 20 furthercomprising: a coordinator component structured and located to allowselective charging and discharging of the rechargeable batteries byselectively controlling the operation of the first and second batterypower converters.
 22. The apparatus of claim 21 wherein the coordinatorcomponent controls the selective charging and discharging of therechargeable batteries so that the first and second batteries dischargeat substantially the same rate with respect to the respective capacitiesof the batteries.
 23. The apparatus of claim 20 wherein the first andsecond battery power converters are structured as DC to DC converterswith buck-boost operation. 24-29. (canceled)